Understanding Capitalization in Writing
English has fifteen situations that require a capital letter. Everything else stays lowercase. Most capitalization mistakes are not missing capitals — they are extra ones, added to words that should have stayed small.
This guide lists every rule with examples, then covers the traps that catch people most often: seasons, job titles, compass directions, family words, school subjects and the rest. It ends with the cases where American and British English genuinely differ.
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The fifteen rules
| # | Capitalize | Example |
|---|---|---|
| 1 | The first word of a sentence | The results arrived. |
| 2 | The pronoun I | She said I was right. |
| 3 | Names of people, and initials | Maria Gonzalez, J. K. Rowling |
| 4 | Places: cities, countries, states, rivers, mountains | Lisbon, Morocco, the Nile |
| 5 | Planets and celestial bodies | Mars, Jupiter, the Milky Way |
| 6 | Days of the week and months | Monday, November |
| 7 | Holidays and named days | Thanksgiving, Election Day |
| 8 | Proper adjectives | Italian food, Victorian houses |
| 9 | Languages, nationalities, ethnic groups | Arabic, Brazilian, Kurdish |
| 10 | Religions and their adherents | Islam, Buddhism, a Catholic |
| 11 | Acronyms and initialisms | NASA, FBI, HTML |
| 12 | Brands, companies, products | Toyota, Microsoft Excel |
| 13 | Historical periods, events, documents | the Renaissance, World War II |
| 14 | Titles directly before a name | President Lincoln, Dr. Chen |
| 15 | The first word of a full-sentence quotation | He said, “We are ready.” |
The traps: words that stay lowercase
This is where most errors happen. Every item below is written correctly in the right-hand column.
| Trap | Wrong | Right |
|---|---|---|
| Seasons | we open in Spring | we open in spring |
| Compass directions | drive North for an hour | drive north for an hour |
| Regions are capitalized | the american south | the American South |
| Job titles after a name | Maria Gonzalez, Director of Sales | Maria Gonzalez, director of sales |
| Job titles without a name | the President spoke | the president spoke |
| School subjects | I study History | I study history |
| Languages as subjects | I study spanish | I study Spanish |
| Family words without a name | I called my Mother | I called my mother |
| Family words as a name | I called mom | I called Mom |
| Centuries and decades | the Twentieth Century | the twentieth century |
| Diseases | he has Diabetes | he has diabetes |
| Diseases named after a person | parkinson disease | Parkinson disease |
| Generic nouns after a proper noun | the Amazon River Basin area | the Amazon river basin area |
| Food and drink | a Cappuccino and a Croissant | a cappuccino and a croissant |
| Foods named after places | french fries, brussels sprouts | French fries, Brussels sprouts |
The substitution test. If a specific name could replace the word, capitalize it. I called Mom works like I called Sarah, so Mom takes a capital. I called my mother cannot become I called my Sarah, so mother stays lowercase. The same test settles Dad, Grandma, Uncle and Doctor.
Capitalization after a colon
The rules differ by style guide, which is why this one causes arguments.
| Style | Rule after a colon | Example |
|---|---|---|
| Chicago | Lowercase, unless what follows is two or more full sentences | She had one aim: to finish. |
| AP | Capitalize if what follows is a complete sentence | She had one aim: She wanted to finish. |
| APA | Capitalize if what follows is a complete sentence | The result was clear: The method worked. |
Pick your organization’s guide and apply it consistently. Nobody notices consistency; everybody notices the third variation on one page.
Capitalizing titles and headings
Titles follow their own system, separate from sentence capitalization. There are three options:
- Sentence case — only the first word and proper nouns. Standard for web headlines, interface text and scientific papers. See the full sentence case rules.
- Title Case — every significant word, with short articles, conjunctions and prepositions left lowercase. Standard for book and film titles. The list of words that stay lowercase is in words that are not capitalized in titles.
- ALL CAPS — short labels only. Never for a heading longer than a few words.
Whether every word in a title should be capitalized is answered in detail in should all letters in a title be capitalized.
Acronyms, initialisms and brand names
Three groups behave differently from ordinary words.
| Type | Rule | Examples |
|---|---|---|
| Initialisms | All capitals, letters pronounced separately | FBI, HTML, USB, PDF |
| Acronyms | All capitals, pronounced as a word | NASA, NATO, UNESCO |
| Absorbed acronyms | Now ordinary words, lowercase | laser, radar, scuba |
| Brand names | However the owner writes them | iPhone, eBay, LEGO, adidas |
A converter that lowercases NASA or turns iPhone into Iphone has failed. Ours detects all-capital words and internal capitals and leaves both alone — see how the two letter forms work in uppercase and lowercase letters explained.
Named days, months and holidays
Days and months always take a capital. So do named holidays and observances: Thanksgiving, Labor Day, Black Friday, Earth Day. Seasons do not, and neither do generic periods such as the holidays or the weekend. The full family of cases, including which election terms are capitalized, is covered in is Election Day capitalized.
American and British differences
| Item | American | British |
|---|---|---|
| Job title before a name | capitalized | capitalized |
| Institution standing alone | the government announced | the Government announced |
| Newspaper headlines | Title Case | Sentence case |
| Spelling of the term itself | capitalization | capitalisation |
The rules themselves barely differ. What differs is headline convention, the treatment of institutions standing alone, and the spelling of the word capitalization.
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Frequently asked questions
What are the main capitalization rules in English?
Capitalize the first word of a sentence, the pronoun I, names of people and places, days, months, holidays, nationalities, languages, religions, brands, acronyms, historical events, and titles used directly before a name.
Are seasons capitalized?
No. Spring, summer, autumn and winter stay lowercase unless they form part of a proper name such as the Summer Olympics.
Do you capitalize job titles?
Only immediately before a name. Write President Lincoln, but Abraham Lincoln, president of the United States, and the president spoke.
Is north capitalized?
Not as a direction: drive north for an hour. Yes as a named region: the American South, Northern Ireland.
Do you capitalize after a colon?
It depends on the style guide. Chicago says lowercase unless two or more full sentences follow. AP and APA say capitalize whenever a complete sentence follows.
Should school subjects be capitalized?
No, with one exception: languages. Write I study history and math, but I study Spanish, because Spanish is a proper adjective.
Do you capitalize mom and dad?
Only when the word replaces a name. I called Mom takes a capital; I called my mom does not.
Are diseases capitalized?
Not in general: diabetes, flu, cancer. Yes when the name contains a proper noun: Parkinson disease, Lyme disease.
The short version
Fifteen rules require a capital: sentence starts, the pronoun I, names, places, days, months, holidays, proper adjectives, languages, religions, acronyms, brands, historical events, titles before a name, and the start of a quoted sentence. Everything else is lowercase, and that includes seasons, compass directions, job titles that follow a name, school subjects other than languages, and centuries. When in doubt, ask whether a specific name could stand in place of the word.